A gyroscope is known as a sensor that detects a rotational angular velocity. A gyroscope that uses a vibrator is called a vibration gyroscope, and the range of uses thereof is wide. For example, the vibration gyroscope is used for sensing camera shake in a video camera, a digital still camera or the like, sensing a direction in a navigation system, sensing an attitude of a mobile unit such as an automobile and an aircraft, and so on.
As signal components outputted from the vibrator of the vibration gyroscope, there are: a drive signal that drives the vibrator; and an angular velocity signal caused by Coriolis force. There is a phase difference of 90 degrees between the drive signal and the angular velocity signal. In the case where an angular velocity occurs in the vibrator, a phase difference between the drive signal and an angular velocity signal outputted from one of two detection electrodes of the vibrator is +90 degrees, and a phase difference between the drive signal and an angular velocity signal outputted from the other is −90 degrees. In the following Patent Citation 1, a vibration gyro circuit, a vibration gyro unit and a vibration gyro output detection method are disclosed, which take a difference between the angular velocity signal outputted from one of the two detection electrodes and the angular velocity signal outputted from the other, and only detect an angular velocity signal thus obtained.
[Patent Citation 1] Japanese Patent Laid-Open Publication No. 2006-105896